There is no right or wrong answer to this question. It will depend on a number of factors.
Fremium's main advantage, is that it allows users to adopt your software easily and before long, you will boast of a large user base. However, on the downside it is capital intensive as you will have to foot the costs for a large number of users who will not be paying anything, thus not generating any direct revenue for you.If you want a very large user base and you have the financial clout to support the cost of the infrastructure needed, then a freemium model will work.
If your software, provides value over time, i.e. the more people use it, the more useful it becomes you should consider freemium. If your software provides value straight away, then a free trial would be the way to go. After the trial period users will fill a void, forcing them to look for alternatives and possibly coming back to purchase the full version. Free trial period is also great if your infrasture can only support a fixed number of people, in which case you will need a small group of loyal customers willing to pay for the service. The software should be compelling for people to want to upgrade to the premium version.
